4 ms·
The radio schematic in the paper looks kind of unusual, with a dual-gate MOSFET. Also a bunch of varactor diodes for tuning. Any radio experts want to comment o
by kens 4y ago
The radio schematic in the paper looks kind of unusual, with a dual-gate MOSFET. Also a bunch of varactor diodes for tuning. Any radio experts want to comment on this circuit? I think it's FM, but I'm not sure.
- formerly_proven 4y agoI don't think that's a radio, just an antenna amplifier. I'm not seeing where demodulation would happen. Some values seem kinda weird to me, like R4 on top of the cascode seems sorta high for something that oughta have a lot of bandwidth (and the way L2+C6 are drawn is odd). Likewise 390k on the emitter of Tr3, seems like very little room for bias for something that's supposed to drive 50 ohms. Bandwidth at the input looks to be <2 MHz, so maybe it's meant for AM broadcast or 160m.
- iasay 4y agoR4 controls the output impedance of TR1. It'd have to be high to keep the loaded Q of the L2 tank high. R10 looks like a mistake to me. Probably should be 390 ohms. Agree with your assertions though. It might have been reverse engineered from something badly or drawn up by someone smoking crack. Even Tektronix had that problem on occasions in their service manuals ...
- iasay 4y ago330uH is a pretty big inductor for FM/VHF. RV1 controls RF gain (think of TR1 as two JFETs, one a current source and one a common source amplifier in a small signal model). TUNE VOLTS changes the resonant frequency of the two tank circuits. TR2/TR3 is an impedance buffer. The rest is decoupling. Looks like a tunable preselector to me rather than a receiver. So part of a receiver yes.